ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...

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ORIGIN AND DIVERSITY OF EAST TEXAS FLORA/INTRODUCTION 225 same species do well in the disturbed habitats of the eastern United States (Stuckey & Barkley 1993). Numerous such European species entered North America at seaport cities along the Atlantic coast and spread westward across the continent (Stuckey & Barkley 1993). An excellent example of this phenomenon can be seen with Chaenorrhinum minus, dwarf snapdragon, which was first observed growing in North America in New Jersey in 1874 (Martindale 1876) and has since spread to over 30 states and nine Canadian provinces (Widrlechner 1983). In some cases, seeds were introduced with soil, sand, or rocks being used as ballast in seagoing ships; Mühlenbach (1979) discussed the role of maritime commerce in dispersal. Other currently problematic taxa were intentionally introduced as ornamentals (e.g., Ligustrum species, privets), as windbreaks (e.g., Tamarix species, salt-cedar), as pasture (e.g., Cynodon dactylon, Bermuda grass), or in misguided attempts at habitat improvement, erosion control, soil stabilization, etc. In yet other cases, exotics are thought to have been accidentally introduced with crop seeds (e.g., Myagrum perfoliatum), hay (e.g., Carduus nutans subsp. macrocephalus), cotton, or wool, or else are species associated with livestock yards. Still others are transported by cars, trucks, or trains (e.g., Chaenorrhinum minus—Widrlechner 1983); Mühlenbach (1979) discussed the importance of railroads as a means of dispersal. The percentage of exotics in the East Texas flora—18% as previously stated—is approximately what would be expected based on data from other parts of the United States. Elias (1977) estimated the level of exotics at 22% in the northeastern United States, and more recently Stuckey and Barkley (1993) indicated that in northeastern states the percentage of foreign species ranged from 20% to over 30%. Their data, compiled from a number of sources, showed that there are higher percentages of foreign species in those states that have been occupied the longest by non-native humans and in those that have been most extensively involved in agriculture. Some northern and western states, with less human influence and disturbance, have figures below 20%. While rather recently colonized by European settlers, East Texas has been extensively cultivated and logged. Nearly all of its habitats have been seriously altered, and numerous exotic species have arrived and become naturalized. Comparable percentages of foreign species are seen in the floras of California (17.5%), Colorado (16%), Iowa (22.3%), Kansas (17.4%), Missouri (27.7%), North Central Texas (17.7%), and North Dakota (15%) (Stuckey & Barkley 1993; Rejmánek & Randall 1994; Diggs et al. 1999; Yatskievych 1999; Yatskievych & Raveill 2001). A disturbing increase in the percentage of exotics can be seen in data from Missouri when comparing tallies from 1963 (Steyermark) and 1999 (Yatskievych). During that 35 year interval, the proportion of non-native components increased from 22.8 to 27.7% (Yatskievych & Raveill 2001). A similar increase is expected to occur in East Texas. Indeed, a significant number of introduced species new to Texas have only recently (since 1997) been reported in East Texas or immediately adjacent areas (i.e., in a non-included portion of a county partly treated in this flora). Some examples are listed in Table 2. Additional exotics can be expected to become part of the East Texas flora in the future, many with serious negative consequences to the remnant native vegetation and to the Texas economy. DIVERSITY (SPECIES RICHNESS) OF THE EAST TEXAS FLORA The 3,402 vascular plant species found in East Texas (slightly more than two-thirds of the total for Texas) make it particularly rich in species for its size (about 62,600 square miles or about 23% of Texas; roughly the size of Georgia). This can be put in perspective when it is realized that the vascular plant flora of the entire Great Plains (which make up one-fifth of the area of the contiguous United States) consists of 3,067 taxa (Great Plains Flora Association 1977, 1986; Thorne 1993d). When the entire flora of North America north of Mexico is considered (estimated at approximately 18,000 species—Thorne 1993d), East Texas includes about one out of every six plant species known in the continental United States and Canada. Likewise, when the number of species in three adjacent states, Arkansas
226 INTRODUCTION/ORIGIN AND DIVERSITY OF EAST TEXAS FLORA (2,877—Arkansas Vascular Plant Manual Committee 2002), Louisiana (2,952—MacRoberts 1984), and Oklahoma (2,549 species—Taylor & Taylor 1994), is considered, East Texas again appears particularly diverse. The striking diversity of the area is also apparent when it is realized that there are 202 vascular plant families (as treated here) in East Texas. This diversity at the family level exceeds all but a handful of states (e.g., Alabama, Florida, Texas). When compared (using the same taxonomic approach to families) with its nearest neighbor to the north, East Texas has 11 more families than all of Oklahoma (Taylor & Taylor 1994), even though Oklahoma is substantially larger. A number of interrelated factors contribute to this diversity: ■ GEOLOGIC AND ASSOCIATED HYDROLOGIC VARIATION resulting in considerable edaphic variation—e.g., very dry to very wet conditions including bogs and baygalls; acidic to calcareous substrates ranging from Carrizo sands to Weches outcrops and Catahoula sandstone; deep highly fertile soils to highly leached areas and rock outcrops. ■ CLIMATIC VARIATION—e.g.,average annual rainfall ranges from nearly 60 inches at the southeastern portion of the area to less than 28 inches at the southwestern margin. ■ HIGH HABITAT DIVERSITY—Large numbers of different habitats occur in a relatively small area, each of these supporting a diverse assemblage of species (this is particularly noteworthy for the Big Thicket; see further discussion on page 164). FIG. 130/ PERCENTAGE OF EASTERN AND WESTERN SPECIES VERSUS LONGITUDE ACROSS TEXAS.(MODIFIED FROM MACROBERTS & MACROBERTS 2003B), WITH PERMISSION OF THE AUTHORS.
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ILLUSTRATED FLORA OF EAST TEXAS
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ALLDREDGE, LINDA & JACK BATTERBAE,
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We would like to recognize and expr
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ISSN 0833-1475 ISBN 1-889878-12-X S
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“DEEP EAST TEXAS IS AN OLD, QUIET
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Elray S. Nixon E lray Nixon was bor
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ILLUSTRATED FLORA OF EAST TEXAS TAB
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TABLE OFCONTENTS/ PAGE APPENDICES A
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Hymenocallis liriosme
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ILLUSTRATED FLORA OF EAST TEXAS OVE
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4 INTRODUCTION/GEOGRAPHIC AREA OF E
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10 INTRODUCTION/MAJOR RIVERS OF EAS
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12 INTRODUCTION/PLANTS TREATED The
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14 INTRODUCTION/GUIDE TO ARRANGEMEN
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16 INTRODUCTION/GUIDE TO SOURCES OF
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18 INTRODUCTION/GUIDE TO GEOGRAPHIC
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20 INTRODUCTION/GUIDE TO ENDANGERED
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22 INTRODUCTION/GUIDE TO GLOSSARY,
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24 INTRODUCTION/GUIDE TO ABBREVIATI
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26 INTRODUCTION/SUMMARY DATA ON FLO
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28 INTRODUCTION/ACKNOWLEDGMENTS Kar
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30 INTRODUCTION/AUTHORS’ NOTE Pre
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32 INTRODUCTION/GENERAL GEOLOGY OF
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46 INTRODUCTION/SOILS SOIL ORDER DE
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48 INTRODUCTION/SOILS, EAST TEXAS B
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50 INTRODUCTION/SOIL-RELATED GEOLOG
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60 INTRODUCTION/SOILS OF BLACKLAND
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66 INTRODUCTION/CLIMATE OF EAST TEX
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Forests define East Texas, and to a
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78 INTRODUCTION/GEOLOGY OF PINEYWOO
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80 INTRODUCTION/PRESETTLEMENT, EARL
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88 INTRODUCTION/PRESETTLEMENT VEGET
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90 INTRODUCTION/CURRENT VEGETATION
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106 INTRODUCTION/POST OAK SAVANNAH
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110 INTRODUCTION/GEOLOGY AND SOILS
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112 INTRODUCTION/SOILS, FIRE, AND T
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114 INTRODUCTION/SOILS, FIRE, AND T
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116 INTRODUCTION/ PRESETTLEMENT, EA
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118 INTRODUCTION/VEGETATION OF POST
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124 INTRODUCTION/CONDITIONS TODAY O
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128 INTRODUCTION/RED RIVER AREA are
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130 INTRODUCTION/BLACKLAND PRAIRIE
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132 INTRODUCTION/GEOLOGY OF BLACKLA
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134 INTRODUCTION/PRESETTLEMENT AND
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144 INTRODUCTION/VEGETATION OF BLAC
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146 INTRODUCTION/FUTURE OF BLACKLAN
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148 INTRODUCTION/FUTURE OF BLACKLAN
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150 INTRODUCTION/CADDO LAKE LOCATIO
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152 INTRODUCTION/CADDO LAKE FIG.84/
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154 INTRODUCTION/PRESENT AND FUTURE
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156 INTRODUCTION/BIG THICKET THE BI
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158 INTRODUCTION/BIG THICKET GEOGRA
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160 INTRODUCTION/NATURAL HISTORY OF
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172 INTRODUCTION/SUMMARY DEFINITION
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